Effects of combined application of high-pressure processing and active coatings on phenolic compounds and microbiological and physicochemical quality of apple cubes

Background: In recent years the use of high-pressure processing (HPP) of fruit products has steadily increased due to its antimicrobial effectiveness and the retention of nutritional and quality attributes compared to conventional thermal technologies. Edible coatings are already being used to enhance the quality of minimally processed fruits. Thus, apple cubes (AC) and alginate-vanillin-coated apple cubes (AVAC) were subjected to HPP (400 MPa/5 min/35 °C). The microbiological and physicochemical parameters were evaluated and the bioactive compounds were monitored before and after HPP of apple cubes. Also, an in vitro gastrointestinal digestion (GID) was conducted.

Results: HPP left L. monocytogenes counts below the detection limit (2 log UFC g^-1 ), regardless of the presence of coating. For E. coli, HPP + active coating showed a synergism affording the greatest reduction (>5 log) for AVAC-HPP. Firmness was maintained in AVAC-HPP samples, while AC-HPP samples suffered reductions of 35%. Colour attributes were also better retained in AVAC-HPP samples. In general, HPP led to a decrease in phenolic compounds. Regarding the effects of GID, vanillin-based active coating exerted a protective effect on some phenolics. Thus, p-coumaroylquinic acid concentration was maintained for AVAC and AVAC-HPP during GID. Epigallocatechin, the compound with the highest concentration in apple cubes, increased for AVAC (106%) and AVAC-HPP (57%). Also, phloridzin concentration increased for AVAC-HPP (17%). At the end of GID, procyanidin B1 and epigallocatechin were the main phenolic compounds for all samples, AVAC showing the highest concentration.

Conclusions: This work demonstrates that the combined application of HPP and active coatings on apple cubes could be used to obtain a safe and good-quality product. © 2021 Society of Chemical Industry.